The present invention relates to systems, equipment and methods for filling and sealing containers, with an air-tight fit to thereby form a shelf-stable product after sterilization thereof. The containers can be, for example, plastic bowls which are filled with chunky or clear soups.
Examples of prior art machines for filling and sealing are the GASTI Cup Filling and Sealing Machine Model DOGAtherm 81 as described in the publication entitled "GASTI Dogatherm" and dated Feb. 17, 1984, and the FEMCO Machine, as described in the publication entitled "4-Head Tandem Gas Flush Heat Seal" and dated September, 1988, and illustrated in the drawings entitled "Gas Flush Extension--Model No. 1250--Serial No. 6469." FEMC is the acronym for Food Equipment Manufacturing Corporation, of Maple Heights, Ohio. These and any other publications, patents or applications mentioned anywhere in this disclosure are hereby incorporated by reference in their entireties.
For both of these machines a continuous, straight line conveying line is provided. Empty containers or packages, such as cups or bowls, are placed in pallets and securely held therein, and conveyed on the conveying line to the filling system, which typically comprises three fill stages. The first is a meat slurry, particulate or ingredient deposit; the second is the vegetable portion deposit; and the third is the broth or water topoff. For products such as chunky clam chowder only a single filling stage or step is needed. The containers are filled approximately ninety percent full of product, as close to the brim as possible. After being filled, the containers are conveyed to the sealing station where lids are placed on the top flange areas thereof and conductive heat sealed thereon. The filled and sealed containers are subsequently sterilized. An example of a sterilizer is the FMC (Food Machine Corp.) Universal Sterilizer, which includes a steam chamber wherein the sealed packages are held for a time sufficient to sterilize the package inside and outside, but not so long as to overcook and degrade the product. The chamber can, for example, be under pressure--twenty-one psi at 250.degree. F.--and the product held therein between an hour and an hour and a half.
The FEMCO and GASTI machines are very similar, and both use similar filling systems. For the FEMCO machine, various numbers of packages can be held in a single pallet. One FEMCO unit has a single line, one package per pallet arrangement, and four sealing heads. The GASTI is a dual line system, with two containers per pallet and in a six-pack arrangement. Thus, the GASTI machine can run at higher speeds than the FEMCO because more, essentially twice, the number of packages are being sealed.
Two methods of sealing lids to the filled containers are known in the prior art. One uses a lid which has been previously dome shaped and cut to the container configuration, positions the pre-cut lid on the container and compresses and heat seals it thereon. The lid can be formed of aluminum foil polypropylene or polyethylene material. Both the FEMCO and GASTI units use this pre-cut lid deposit technique. A second method is a continuous foil lid operation where a sheet of foil is placed on the bowl flange, and a blade is lowered down and cuts or serates the excess foil off, thereby shaping the lid to the bowl, as the foil is compressed and heat sealed to bowl. With either of these techniques and prior to fusing the lid material to the bowl flange, a vacuum can be pulled out according to the prior art and nitrogen gas injected into the bowl as the lid is placed on top of the bowl and immediately prior to sealing. In other words, a vacuum is pulled out, inert gas is injected under the lid into the package and the lid then heat sealed in place.
After the lid has been sealed to the container, the sealed package is put through a sterilization process. This gives the package a shelf life of a year to two and a half years without loss of flavor. Examples of products made by this system are those available from Campbell Soup Company of Camden, New Jersey, including their "Microwavable Chunky Soup--Ready To Serve," which comes in five varieties--sirloin burger, chicken, old fashioned chicken, clam chowder and beef noodles.
During the filling stage and as additional product is added into the package, container or bowl the target area or depth in the container gets smaller. Meats, vegetables and other contaminants are thereby more likely to be deposited on the flange area of the containers. Further deposition results from the splashing caused when the frozen or heated products impact one another and also from condensation droplets.
When contaminants or any other particulates are on the flange, a perfect seal and fusion of the lid thereto cannot be guaranteed. The seals of the present product are not the same as those found on many frozen products wherein the seal functions essentially as a dust cover. Rather, heating or fusing is used therein to provide a perfect air-tight seal. After the seal is on, the package is sterilized as previously described and a shelf-stable product created. An air-tight seal is created keeping the contents inside of the package sealed and not allowing anything else to get into the package or the contents thereof to spoil. Additionally, during sterilization of the sealed package, lid and/or flange expansion and contraction can occur, and if there is not a good fusion and a good seal, the seal can open. In other words, even if a seal is made around the entire perimeter of the flange initially, the seal may release itself at a later date, if there are any particulates or liquids on the flange area. If the seal releases, the opening thereby formed can result in the particulates, liquids and ingredients decaying or otherwise contaminating the product, or allowing foreign materials into the package.
Removal of the contaminants from the container flange after the filling stage and before the sealing stage can thus be critical. In the past this has been done manually. One or more workers are positioned along side the conveying line and as the filled containers pass by them, the workers manually wipe the flanges off with paper towels. This manual cleaning process is obviously labor intensive and thus expensive and slow, and perfect cleaning cannot always be guaranteed.
A process for sealing glass bottles is disclosed in U.S. Pat. No. 4,771,903. When these bottles are filled with wet, pulpy material such as orange juice, grapefruit juice and tomato juice, the pulpy semi-solid residues on the container rim can reduce the effectiveness of the seal closure. Mention is made in that patent that to reduce the amount of pulpy residue from the rim prior to sealing a post-heat treatment can be used. This heat treatment renders the rim surface more hydrophobic, and the pulpy liquids and solids are thus less likely to stick to the rim and more likely to be squeezed out from between the surfaces during the sealing process. The preferred cleaning method disclosed in that patent, however, subjects the container rim to a fluid stream directed across the surfaces of the rim. The stream comprises an intermittent jet of steam or hot air directed inwardly or horizontally across the flange. This cleaning method avoids physical wiping or brushing of the rim to remove the pulpy residues which in itself can lead to contamination and does not provide as complete a hermetic sealing surface. A plastic cap, instead of metal foil seals of the type shown in U.S. Pat. No. 4,260,438, are then applied to the bottle rim.